The present invention relates generally to providing network services such as load balancing, packet filtering, or Network Address Translation (NAT). Network services are provided using service managers that are integrated into a routing infrastructure.
As the IP protocol has continued to be in widespread use, a plethora of network service appliances have evolved for the purpose of providing certain network services not included in the protocol and therefore not provided by standard IP routers. Such services include NAT, statistics gathering, load balancing, proxying, intrusion detection, and numerous other security services. In general, such service appliances must be inserted in a network at a physical location where the appliance will intercept all flows of interest for the purpose of making its service available.
FIG. 1 is a block diagram illustrating a prior art system for providing a network service. A group of clients 101, 102, and 103 are connected by a network 110 to a group of servers 121, 122, 123, and 124. A network service appliance 130 is physically located in the path between the clients and the servers. Network service appliance 130 provides a service by filtering packets, sending packets to specific destinations, or, in some cases, modifying the contents of packets. An example of such modification would be modifying the packet header by changing the source or destination IP address and the source or destination port number.
Network service appliance 130 provides a network service such as load balancing, caching, or security services. In providing security services, network service appliance 130 may function as a proxy, a firewall, or an intrusion detection device. For purposes of this specification, a network service appliance that acts as a load balancer will be described in detail. It should be noted that the architecture and methods described are equally applicable to a network service appliance that is functioning as one of the other above described devices.
Network service appliance 130 is physically located between the group of servers and the clients that they serve. There are several disadvantages to this arrangement. First, it is difficult to add additional network service appliances when the first network service appliance becomes overloaded because the physical connections of the network must be rerouted. Likewise, it is difficult to replace the network service appliance with a back up network service appliance when it fails. Since all packets pass through the network service appliance on the way to the servers, the failure of the network service appliance may prevent any packets from reaching the servers and any packets from being sent by the servers. Such a single point of failure is undesirable. Furthermore, as networks and internetworks have become increasingly complex, multiple services may be required for a single network and inserting a large number of network service appliances into a network in places where they can intercept all relevant packet flows may be impractical.
The servers may also be referred to as hosts and the group of servers may also be referred to as a cluster of hosts. If the group of servers has a common IP address, that IP address may be referred to as a virtual IP address (VIPA) or a cluster address. Also, it should be noted that the terms client and server are used herein in a general sense to refer to devices that generally request information or services (clients) and devices that generally provide services or information (servers). In each example given it should be noted that the roles of client and server may be reversed if desired for a particular application.
A system that addresses the scalability issues that are faced by network service appliances (load balancers, firewalls, etc.) is needed. It would be useful to distribute functions that are traditionally performed by a single network element and so that as much function as possible can be performed by multiple network elements. A method of coordinating work between the distributed functions with a minimum of overhead is needed.
Although network service appliances have facilitated the development of scalable server architectures, the problem of scaling network service appliances themselves and distributing their functionality across multiple platforms has been largely ignored. Network service appliances traditionally have been implemented on a single platform that must be physically located at a specific point in the network for its service to be provided.
For example, clustering of servers has been practiced in this manner. Clustering has achieved scalability for servers. Traditional multiprocessor systems have relatively low scalability limits due to contention for shared memory and I/O. Clustered machines, on the other hand, can scale farther in that the workload for any particular user is bound to a particular machine and far less sharing is needed. Clustering has also facilitated non-disruptive growth. When workloads grow beyond the capacity of a single machine, the traditional approach is to replace it with a larger machine or, if possible, add additional processors within the machine. In either case, this requires downtime for the entire machine. With clustering, machines can be added to the cluster without disrupting work that is executing on the other machines. When the new machine comes online, new work can start to migrate to that machine, thus reducing the load on the pre-existing machines.
Clustering has also provided load balancing among servers. Spreading users across multiple independent systems can result in wasted capacity on some systems while others are overloaded. By employing load balancing within a cluster of systems the users are spread to available systems based on the load on each system. Clustering also-has been used to enable systems to be continuously available. Individual application instances or machines can fail (or be taken down for maintenance) without shutting down service to end-users. Users on the failed system reconnect and should not be aware that they are using an alternate image. Users on the other systems are completely unaffected except for the additional load caused by services provided to some portion of the users that were formerly on the failed system.
In order to take full advantage of these features, the network access must likewise be scalable and highly available. Network service appliances (load-balancing appliances being one such example) must be able to function without introducing their own scaling limitations that would restrict the throughput of the cluster. A new method of providing network services using a distributed architecture is needed to achieve this.
Network services such as load balancing, packet filtering, or Network Address Translation (NAT) are traditionally performed by single boxes that must be installed directly in the data path of the packets that are being processed. This limits the scalability of the service to the capacity of a single box that is inserted in the data stream. If multiple service managers are required to handle a large load, then partitioning of the work is done by the client population. For example, if multiple parallel firewalls are needed to protect a site, then clients must be individually configured to use a firewall or must somehow be assigned to a certain firewall when needed. What is needed is an architecture that allows multiple network service appliances to be configured in parallel to provide network services. Ideally, service appliances could partition a client population among themselves and repartition the population as needed given changing load conditions. Removing control from the clients would create a more stable, controllable, and predictable network environment.
A system that includes a plurality of service managers that provide network services through forwarding agents implemented on routers is disclosed. Service managers are partitioned among various clients by configuring the servers to process packets from certain clients. Service managers intercept packets and perform various actions on the packets by using a set of forwarding agents that send packets to the service managers and receive instructions from the service managers that enable the forwarding agents to perform various functions without having the logic required to determine the necessary actions. A plurality of service managers send packet forwarding requests to the same set of forwarding agents. All packets transferring through the forwarding agents may be partitioned among the service managers for determination of appropriate actions and instructions for the forwarding agents.
It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, or a computer readable medium such as a computer readable storage medium or a computer network wherein program instructions are sent over optical or electronic communication lines. Several inventive embodiments of the present invention are described below.
In one embodiment, a method of partitioning a network service among a plurality of service managers includes configuring a first service manager to send a first request to a forwarding agent for packets meeting a first criteria and sending the first request to the forwarding agent. A second service manager is configured to send requests to the forwarding agent for packets meeting a second criteria and the second request is sent to the forwarding agent. Packets are checked at the forwarding agent to determine whether the packets meet the first criteria or the second criteria and packets that meet the first criteria are received at the first service manager; and packets that meet the second criteria are received at the second service manager.
In another embodiment, a service manager is configured to send a wildcard affinity update packet to a forwarding agent. The wildcard affinity update packet includes a wildcard affinity that includes a specification of a set of source IP addresses, a specification of a set of destination IP addresses, and a time to live and instructions that indicate that a packet matching the wildcard affinity is to be sent to the service manager.
In another embodiment, a forwarding agent includes a service manager receiving interface configured to receive a plurality of requests from a plurality of service managers for packets meeting a plurality of criteria and a network interface configured to receive packets from devices on a network. A processor is configured to check the packets to determine whether the packets meet one of the plurality of criteria and a service manager sending interface is configured to send packets that meet one of the plurality of criteria to one of the plurality of service managers that corresponds to the one of the plurality of criteria.
In another embodiment, a method of handling packets includes receiving a plurality of requests from a plurality of service managers for packets meeting a plurality of criteria and receiving packets from devices on a network. The packets are checked to determine whether the packets meet one of the plurality of criteria and packets that meet one of the plurality of criteria are sent to one of the plurality of service managers that corresponds to the one of the plurality of criteria.
These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and the accompanying figures which illustrate by way of example the principles of the invention.